[Rockhounds] Coprolites

[Tim Fisher]

I am repeating what was posted by Tom, combined with observations 
from years of collecting Salmon creek. I have never witnessed, nor 
have I heard of anyone collecting, any ropy, smooth surfaced nodules 
in the Wilkes Fm. clay. They are all found in the stream gravels. The 
un-eroded nodules in the clay are as Tom describes them, lumpy, with 
a very convoluted, intricate surface.

At 09:09 PM 4/8/2008, you wrote:
>
>In a message dated 4/8/2008 9:56:11 PM Mountain Daylight Time,
>nospam at orerockon.com writes:
>
>The  fresh, un-eroded concretions are iron oxide, the eroded
>concretions have  been oxidized in the air and in the stream to iron
>siderite. The  explanation is quite simple. Get some concretions from
>the un-eroded clay  in the Wilkes, and from the stream bed. Analyze
>both. Then you will see  that the "poopy" iron siderite nodules are
>simply eroded forms of the iron  oxide nodules.
>
>
>
>No, sorry, that can't be it.  Siderite (ferrous iron carbonate, FeCO3)
>oxidizes to limonite, not the other way around.
>
>Pete
>
>(never been to the locality, but I'm pretty sure that a specimen or two  that
>I've purchased over the years, must be from  there)
>

Tim Fisher Ore-ROCK-On!
Web Site: http://OreRockOn.com